Surgical burring tool

ABSTRACT

An orthopedic burring tool includes a burring tip configured for removal of bone to form a bore in the bone, an elongated intermediate segment having a smooth outer surface along a length of the segment, a conical widening segment at the proximal end of the intermediate segment that widens from the diameter of the burring tip to a diameter that is about twice the burring tip diameter. The widening segment includes an outer surface configured for removal of bone upon rotation of the burring tool. The tool includes an upper segment configured for engagement to a rotary driving tool and having a cylindrical outer surface configured for removal of bone upon rotation of the burring tool for removal of material from bony structure adjacent the bone bore formed by the burring tip.

PRIORITY CLAIM

This application is a utility filing of and claims priority to U.S.provisional application No. 62/875,751, filed on Jul. 18, 2019, theentire disclosure of which is incorporated herein by reference.

BACKGROUND

Spinal fixation systems rely on anchoring stabilization components tothe vertebral body. In one approach, the stabilization components areanchored by bone screws or bolts introduced into the vertebral body,such as along the pedicle. In a common procedure, the vertebral bone isprepared for the introduction of the bone screw by drilling a bore intothe vertebral body and then threading the screw or bolt BT into thatbore, as shown in FIGS. 3A-3B. A burring tool is used to prepare thebore. Burr guides are often used to ensure that the burring tool isadvanced on a proper line into the vertebral body. This is aparticularly important consideration in preparing a bore through thepedicle to ensure that the bore is solidly contained within the pedicleand that the bore does not deviate from the pedicle into the vertebralforamen.

In addition, in many fixation installations, the bone screw/bolt BTincludes a “tulip” head TL configured to receive an elongated spinalrod, as shown in FIGS. 3A-3B. The spinal rod is bent to a desiredcontour so that the patient's spine adopts the desired contour when thespinal rod is anchored to the spine. The tulip head TL receives alocking screw L to lock the rod to the bone screw/bolt BT. The tuliphead includes a generally spherical bottom surface S that contacts thevertebral bone when the bone screw/bolt is fully engaged within thevertebral body. Thus, in addition to preparing the opening using aburring tool, an additional tool is often used to contour the surface ofthe bone to receive the tulip head of the bones screw/bolt. However,since a different tool is used to contour the bone surface, in someinstances the surface contouring can deviate from the path of the boreso that the contoured surface does not accept the tulip head of the bonescrew when it is introduced into the bore.

In addition, in order to permit the bone screw to be advanced into theprepared bore, it is often necessary to remove bone adjacent to theinsertion site. Thus, yet another burring tool is often used to removebone from the facet joint F or transverse process TP that might be alongthe axis of introduction of the bone screw/bolt.

There is a need for a tool that can prepare the entire site forintroduction of a bone bolt, without the need to use separate tools.There is also a need for a tool that can ensure proper orientation ofthe prepared bone surface with a bore formed in the bone.

SUMMARY OF THE DISCLOSURE

An orthopaedic burring tool includes an elongated intermediate segmenthaving a smooth outer surface along a length of the intermediate segmentand a burring tip connected to the distal end of the intermediatesegment. The burring tip has an outer surface configured to remove boneupon rotation of the burring tool to form a bore in the bone. The toolfurther includes a conical widening segment connected to the proximalend of the intermediate segment. The widening segment increases indiameter from the diameter of the burring tip to a larger diameter atthe proximal end of the widening segment that can be about twice thediameter of the burring tip. The widening segment has an outer surfaceconfigured for removal of bone upon rotation of the burring tool.

The burring tool further includes an upper segment configured forengagement to a rotary driving tool and connected to the proximal end ofthe widening segment. The upper segment is cylindrical and has adiameter greater than largest diameter of the widening segment. Theupper segment has a cylindrical outer surface configured for removal ofbone upon rotation of the burring tool to remove material from a bonystructure adjacent the site of introduction of the burring tool into thebone. When the burring tool is used to prepare a pedicle of a vertebrafor introduction of a bone screw/bolt, the burring tip creates the boreand the widening segment creates a funnel-shaped opening for the bore toreceive the distal surface of the tulip head of the bone bolt. The uppersegment removes material from an adjacent bony structure to provideclearance for introduction of the pedicle screw.

DESCRIPTION OF THE FIGURES

FIG. 1 is a side view of a burring tool according to one embodiment ofthe present disclosure.

FIGS. 2A-2C a view in the transverse plane of a vertebral body showingsuccessive steps of the introduction of the burring tool shown in FIG. 1into the pedicle of the vertebra.

FIGS. 3A-3B are views in the transverse and sagittal planes of a lumbarvertebra with a bone bolt placed in the pedicles of the vertebra.

FIG. 4A is an end view of the burring tip of the burring tool shown inFIG. 1 and depicting the bi-directional cutting edges of the burring tipaccording to one embodiment of the disclosure.

FIG. 4B is a partial cross-sectional view of the burring tool taken atthe interface between the intermediate segment and the widening segmentof the burring tool shown in FIG. 1 and depicting bi-directional cuttingedges of the widening segment according to one embodiment of thedisclosure.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of thedisclosure, reference will now be made to the embodiments illustrated inthe drawings and described in the following written specification. It isunderstood that no limitation to the scope of the disclosure is therebyintended. It is further understood that the present disclosure includesany alterations and modifications to the illustrated embodiments andincludes further applications of the principles disclosed herein aswould normally occur to one skilled in the art to which this disclosurepertains.

The present disclosure provides a burring tool that ensures alignment ofthe surface contour with the bone screw bore and that automaticallyprepares adjacent bone for introduction of the bone screw/bolt BT. Asshown in FIG. 1, the burring tool 10 includes a burring tip 11 that canbe configured like a conventional burring tool for spinal surgicalapplications. In particular, the burring tip can include a series ofhelical or spiral cutting flutes around the circumference of the tip.The burring tip 11 is integral with the distal end of an elongatedsmooth intermediate segment 12, with the smooth shaft having the sameouter diameter as the burring tip. In one specific embodiment, the outerdiameter is 3 mm to prepare a bore for receiving a conventionally sizedbone screw or bolt. In one specific embodiment, the burring tip 11 has alength L3 of about 3 mm and the smooth intermediate segment 12 has alength L4 of about 15 mm.

The proximal end of the smooth intermediate segment 12 is integral witha conical widening segment 13 in which the diameter of the tool 10gradually increases from the diameter of the burring tip at the distalend of the widening segment to a diameter at the opposite proximal endof the segment that is sized to receive the intermediate portion of thebone screw/bolt and the base of the tulip head of the bolt/screw. In onespecific embodiment, the widening segment 13 is configured to removebone and in particular to widen the opening in the bone from the 3 mm ofthe burring tip to about 6 mm. The widening segment 13 has a length L2,which can be about 10 mm and subtends a conical angle of about 15-25degrees in one specific embodiment. The overall length L1 of the bonebore preparing surfaces 11, 12, 13 of the burring tool 10 can be 28-30mm in specific embodiments for the preparation of a bore in the pedicleof a lumbar vertebral body. Other overall lengths L1 are contemplateddepending on the vertebral level being prepared. The average pediclelength for the L5 vertebra is about 24 mm, but can vary ±7 mm, sodifferent overall lengths L1 are necessary. The pedicle lengths of thethoracic vertebrae range from 4.5 mm at T4 to 10 mm at T12, so againdifferent overall lengths L1 are dictated. Likewise, for the cervicalspine.

The burring tool 10 terminates in an upper segment 14 integral with thewidening segment 13 by a transition segment 15. The upper segment isgenerally cylindrical and has a larger outer diameter than the remainderof the burring tool 10 because the upper segment 14 is arranged toremove material from bony structure adjacent the insertion site of thebone screw/bolt. Thus, in one specific embodiment, the upper segment 14has a diameter of 10 mm and a length of about 5 mm. The transitionsegment 15 is thus configured to transition between the two diametersand is preferably conical over a length of 1-2 mm. Like the burring tip11 and the widening segment 13, the upper segment 14 is configured toremove bone.

The upper segment 14 is configured to be mounted to a rotary drivingtool for high-speed rotation of the burring tool. Thus, the uppersegment can include a threaded bore or a projecting stem configured toengage a rotary driving tool in a known manner. It is contemplated thatthe burring tool can include a central bore along its length forintroduction of the tool along a guide wire or K-wire to ensure that thebore is prepared at the proper angle within the vertebral body.

The diameters of the bone removing surfaces can be modified as neededbased on location of the bone bore being created. The first diameter—thediameter of the burring tip—can be equal to a second diameter—thesmaller diameter of the widening segment. A third diameter—the largerdiameter of the widening segment—can be twice the first diameter. Afourth diameter—the diameter of the cylindrical upper segment—can be atleast three times the first diameter.

Use of the burring tool 10 is depicted in FIGS. 2A-2C. In the initialstep, the burring tool 10, mounted on a driving tool T, is introducedalong a desired bore axis A through the pedicle P of a vertebral bodyVB. The tool 10 is advanced along the axis A into the bone until theupper segment 14 contacts the adjacent bony structure, as shown in FIG.2B. As the burring tool is advanced further into the vertebral body VB,the upper segment removes material from the adjacent bony structure,providing a clear path for introduction of the bone screw/bolt, as shownin FIG. 2C. As the burring tool is advanced along the bore axis A, theburring tip 11 creates a path for the tool 10 through the bone. Thesmall burring tip is advantageous for providing a precise starting pointand trajectory for the bore axis A with minimal deflection of the tool,even at high introduction angles. In conventional approaches, as theburring tool is advanced further into the bone the tool tends to deflector deviate from the desired path. The tool 10 of the present disclosureavoids that problem with the smooth intermediate segment 12 whichcontacts the wall of the newly-prepared bore created by the burring tip.Since the intermediate segment 12 is smooth it does not impede theadvancement of the tool into the bone as the burring tip 11 is drivenfurther into the bone. Instead, the intermediate tip acts as a bearingsurface or burr guide to maintain the proper orientation of the burringtool 10 and to prevent deflection of the tool as the tip moves deeperinto the bone.

Eventually the widening segment 13 contacts the bone and begins toenlarge the upper portion of the bore B in the bone, as depicted in FIG.2C. The intermediate segment 12 helps maintain the proper alignment ofthe tool along the axis A even as the upper portion of the bore is beingwidened. After the burring tool has been advanced to the desired depth,the resulting bore B is configured to accept the bone screw/bolt with awidened funnel shaped portion W at the bone surface to accommodate thetulip head TL of the bone screw/bolt BT (FIG. 3A). The diameter of thewidened portion W can be determined by the distal surface of the tuliphead TP, and that diameter is ultimately determined by the depth thatthe burring tip 11 is introduced into the bone. After the burring toolhas advanced to its desired depth to create the bore B, the uppersegment 14 has removed adjacent bone, as shown in FIG. 2C so that thebone screw/bolt can be readily threaded into the prepared bore withoutinterference from adjacent vertebral bony structure.

It is contemplated that the burring tool 10 is an integrally formedstructure. However, it is also contemplated that the segments of thetool can be separate and engaged to each other to form the completetool. Thus, two or more of the burring tip 11, intermediate segment 12,conical widening segment 13 and upper segment 14 can be separatecomponents that can be combined to form the tool 10. It is contemplated,for instance, that different lengths of intermediate segments 12 can beprovided for engagement with a common burring tip 11 depending on lengthof the bone bore to be created. Likewise, different lengths of wideningsegments 13 may be provided for use in a similar manner.

As explained above, the tool 10 is configured to be driven by a rotarydriving tool for high-speed rotation of the tool. In one embodiment, thetool is rotated in one direction during the process for preparing thebone bore. In another embodiment, the tool can be bi-directional,meaning that it can be rotated in either the clockwise orcounter-clockwise directions. In this embodiment, one or more of thebone preparing surfaces 11, 13, and 14 can be configured for differentbone removal characteristics depending upon the direction of rotation.Thus, in the conventional driving direction (clockwise), the surface isconfigured for rapid removal of bone, whereas in the opposite direction(counter-clockwise), the surface if configured for fine bone removal toproduce a smooth prepared surface of the bone. This attribute can beparticularly advantageous for the funnel-shaped portion W of the bonebore B which receives the distal surface S of the tulip head TL. In oneembodiment, shown in FIG. 4A, the burring tip 11 can incorporate thebi-directional bone preparing surface. In a particular, the surfaceincludes an aggressive cutting edge 20 that is curved to increase thelength of the edge. The edge 20 is generally concave in the direction ofrotation, which is clockwise as viewed in FIG. 4A. The edge 20 isdefined by an inclined surface 20 a that extends from the primarysurface 11 a of the burring tip. In a specific embodiment, the cuttingedge 20 can project a height of 0.3 mm from the surface 11 a. In theillustrated embodiment, the burring tip 11 is provided with twoaggressive cutting edges 20 spaced 180° apart.

The burring tip includes a less aggressive cutting edge 22 that facesthe other direction of rotation, which is counter-clockwise in thefigure. The edge 22 is generally straight and indented from the outeredge of the burring tip 11. The edge 22 is at the end of an inclinedsurface 22 a projecting from the primary surface 11 a of the burringtip. In a specific embodiment, the less aggressive cutting edge canproject a height of 0.2 mm from the surface 11 a. In other embodiments,the less aggressive cutting edges can project a height above the primarysurface that is ½-⅔ the height of the aggressive cutting edges. In theillustrated embodiment, two edges 22 are situated between the twoaggressive cutting edges 20. It is understood that when the burring toolis rotated in the clockwise direction (as viewed in the figures), onlythe aggressive cutting edges 20 will remove material from the bone. Whenthe burring tool is rotated in the opposite (counter-clockwise)direction, only the less aggressive cutting edges 22 will removematerial from the bone. Since the cutting edges 22 are less prominentthan the aggressive cutting edges 20, the material removed in a givenfull rotation in the counter-clockwise direction will be less than thematerial removed by the aggressive edges in a full clockwise rotation.

The same principle can be applied at the surface 13 a of the wideningportion 13, as shown in FIG. 4B. Thus, the widening portion can includeaggressive cutting edges 20′ and less aggressive cutting edges 22′extending from the interface with the intermediate segment 12 to theinterface with the transition segment 15. The edges 20′ are configuredin a similar manner to the edges 20, and the edges 22′ are configured ina similar manner to the edges 22, so that greater bone material isremoved for clockwise rotation (in the specific example) than is removedfor counter-clockwise rotation. As noted above, the aggressive cuttingedges 20′ of the widening segment 13 can initially prepare thefunnel-shaped portion W of the bone opening, followed by reverserotation and use of the less aggressive cutting edges 22′ to provide asmooth surface to the portion W to receive the tulip head of the bonebolt. In the embodiment shown in FIG. 4b , four cutting edges 20′ andfour cutting edges 22′ are distributed uniformly around thecircumference of the surface 13 a. Other numbers of cutting edges arecontemplated. The same cutting edge structure can be applied to the boneremoving surface of the upper segment 14.

The present disclosure should be considered as illustrative and notrestrictive in character. It is understood that only certain embodimentshave been presented and that all changes, modifications and furtherapplications that come within the spirit of the disclosure are desiredto be protected.

1-15. (canceled)
 16. A surgical system comprising: an instrumentextending along a longitudinal axis between opposite proximal and distalends, the distal end including a tip extending parallel to thelongitudinal axis and having a first cutting surface, the proximal endincluding a portion extending transverse to the longitudinal axis, theportion having a second cutting surface, the instrument including anintermediate segment between the cutting surfaces, the intermediatesegment including a smooth outer surface.
 17. The surgical systemrecited in claim 16, wherein the proximal end is configured forengagement with a rotary driving tool for rotation of the instrumentabout the longitudinal axis, the system further comprising the rotarydriving tool.
 18. The surgical system recited in claim 16, wherein theproximal end includes a threaded bore configured for engagement with arotary driving tool for rotation of the instrument about thelongitudinal axis, the system further comprising the rotary drivingtool.
 19. The surgical system recited in claim 16, wherein the proximalend includes a projecting stem configured for engagement with a rotarydriving tool for rotation of the instrument about the longitudinal axis,the system further comprising the rotary driving tool.
 20. The surgicalsystem recited in claim 16, wherein the tip has a first diameter, adistal section of the portion having a second diameter that issubstantially equal to the first diameter, an opposite proximal sectionof the portion having a third diameter that is greater than the firstdiameter.
 21. The surgical system recited in claim 16, wherein the firstcutting surface includes a series of flutes around a circumference ofthe tip.
 22. The surgical system recited in claim 16, wherein the firstcutting surface includes a series of helical flutes around acircumference of the tip.
 23. The surgical system recited in claim 16,wherein the first cutting surface includes a series of spiral flutesaround a circumference of the tip.
 24. The surgical system recited inclaim 16, wherein the portion includes aggressive cutting edges orientedto remove material from bone in one direction of rotation of theinstrument and less aggressive cutting edges oriented to remove materialfrom bone in an opposite direction of rotation of the instrument. 25.The surgical system recited in claim 24, wherein the bone materialremoved by the less aggressive cutting edges in one full rotation in theopposite direction of rotation is less than the bone material removed bythe aggressive cutting edges in one full rotation in the one directionof rotation.
 26. The surgical system recited in claim 24, wherein thefirst cutting surface includes a series of flutes around a circumferenceof the tip.
 27. The surgical system recited in claim 16, wherein theportion is conical.
 28. The surgical system recited in claim 16, whereinthe smooth outer surface extends continuously from the first cuttingsurface to the second cutting surface.
 29. A surgical system comprising:an instrument extending along a longitudinal axis between oppositeproximal and distal ends, the distal end including a tip extendingparallel to the longitudinal axis and having a first cutting surface,the proximal end including a first portion extending parallel to thelongitudinal axis and a second portion extending transverse to thelongitudinal axis, the second portion being positioned between the firstportion and the distal end, the second portion having a second cuttingsurface, the instrument including an intermediate segment between thecutting surfaces, the intermediate segment including a smooth outersurface; and a driving tool configured for engagement with the firstportion to rotate the instrument about the longitudinal axis.
 30. Thesurgical system recited in claim 29, wherein the second portion includesaggressive cutting edges oriented to remove material from bone in onedirection of rotation of the instrument and less aggressive cuttingedges oriented to remove material from bone in an opposite direction ofrotation of the instrument.
 31. The surgical system recited in claim 30,wherein the bone material removed by the less aggressive cutting edgesin one full rotation in the opposite direction of rotation is less thanthe bone material removed by the aggressive cutting edges in one fullrotation in the one direction of rotation.
 32. The surgical systemrecited in claim 30, wherein the first cutting surface includes a seriesof flutes around a circumference of the tip.
 33. The surgical systemrecited in claim 30, wherein the first cutting surface includes a seriesof helical flutes around a circumference of the tip.
 34. The surgicalsystem recited in claim 30, wherein the first cutting surface includes aseries of spiral flutes around a circumference of the tip.
 35. Asurgical system comprising: an instrument extending along a longitudinalaxis between opposite proximal and distal ends, the instrumentcomprising a central bore along its length for introduction of theinstrument along a guide wire, the distal end including a tip having afirst cutting surface, the proximal end including a first portionextending parallel to the longitudinal axis and a second portionextending transverse to the longitudinal axis, the first portionincluding a threaded bore, the second portion being positioned betweenthe first portion and the distal end, the second portion having a secondcutting surface, the instrument including an intermediate segmentbetween the cutting surfaces, the intermediate segment including asmooth outer surface extending continuously from the first cuttingsurface to the second cutting surface; and a driving tool configured forengagement with the threaded bore to rotate the instrument about thelongitudinal axis, wherein the second portion includes aggressivecutting edges oriented to remove material from bone in one direction ofrotation of the instrument and less aggressive cutting edges oriented toremove material from bone in an opposite direction of rotation of theinstrument.